Technical Field
The present disclosure relates to the field of semiconductor structures and, more particularly, to bipolar transistors and products that include bipolar transistors.
Description of the Related Technology
Bipolar transistors, such as heterojunction bipolar transistors (HBTs), are implemented in a wide variety of applications. Such bipolar transistors can be formed on semiconductor substrates, such as gallium arsenide (GaAs) substrates. One illustrative application for a bipolar transistor is in a power amplifier system. Specifications for power amplifier systems have become more demanding to meet.
One aspect of transistor performance is linearity. Linearity can also be a measure of performance of a power amplifier system. Measures of linearity performance can include channel power ratios, such as an adjacent channel power ratio (ACPR1) and an alternative channel power ratio (ACPR2), and/or channel leakage power ratios, such as an adjacent channel leakage power ratio (ACLR1) and an alternative channel leakage power ratio (ACLR2). ACPR2 and ACLR2 can be referred to as second channel linearity measures. ACPR2 and ACLR2 values can correspond at measurements at an offset of about 1.98 MHz from a frequency of interest.
Another aspect of transistor and/or power amplifier system performance is safe operating area (SOA). SOA can be determined from a breakdown voltage of a transistor, such as BVCEO. BVCEO can represent a breakdown voltage from collector to emitter with an open circuit at the base. BVCEO can be a direct current (DC) measurement.
A need exists for transistors with improved linearity and/or SOA in a variety of systems, such as power amplifier systems.